An Iranian airliner carrying medical supplies and aid workers landed Sunday in the Yemeni capital, Sana'a, less than 24 hours after Shi'ite rebels controlling the city signed an aviation pact with Tehran.

Witnesses say senior Iranian diplomats were on hand to greet the flight -- the first since Shi'ite rebel Houthis seized control of the capital in January and placed Sunni President Abed Rabbo Mansour Hadi under house arrest.

Yemen's official Saba News Agency -- now controlled by the Shi'ite militia -- said 14 weekly flights will connect Tehran and Sana'a.

However, ousted U.S.-backed President Hadi, who fled detention earlier this month to a new base in the southern city of Aden, said those who signed the pact will, in his words, "be held accountable." On Saturday, Mr. Hadi rejected the Shi'ite takeover of the city, in a statement issued under the title of president.

The statement, read on pan-Arabic Al-Jazeera television, signaled an apparent retraction of the resignation he announced last month after rebels seized the presidential palace in Sana'a.

U.S. Secretary of State John Kerry last week linked the collapse of Yemen's Sunni government to "critical" pressure by the northern-based Houthi militia, which has long clashed with Sana'a government leaders.

The Houthi takeover of the capital triggered a mass exodus of foreign diplomats. It also prompted calls from the United Nations Security Council for the restoration of the Hadi government, and for dialogue aimed at preventing the country from sliding into civil war.